Composite dome connectors for flywheel rim to shaft attachment

ABSTRACT

A dome connector for a flywheel rim to shaft attachment is provided. The dome connector includes a helically wound composite band that extends from a first port to a second port. The helically wound composite band has a helical angle in relation to a line perpendicular to a center of axis of the dome connector. The helical angle is selected to at least in part achieve a desired stiffness in the dome connector.

BACKGROUND

Composite flywheels such as carbon composite flywheels are desired because they are strong while having a light weight (this is known as having a high specific strength). It is common for the composite flywheels to be connected to a metal shaft for the purpose of putting in or taking out kinetic energy from the flywheel. A common limiting factor for high performance carbon composite flywheels, or other high strength fiber composite flywheels, is the connection of the radially expanding (high strained) flywheel rim to the metal shaft which expands much less (due to its smaller diameter). Typical composite/metal connections do not have sufficient stress/strain capabilities and connections, such as geometrically compliant metal spokes, lead to dynamic instability. Moreover, connecting flat composite plates, with fiber oriented in the radial direction or near radial direction, form a shaft to rim connection which produces unmanageable bond/fastener stresses. In addition, using very thick filament wound disks (with a majority of the fibers in the circumferential direction) results in unacceptable radial tensile stresses (across ply stresses) occurring in the hub.

For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an effective, efficient and dynamically stable flywheel to shaft connection.

SUMMARY OF INVENTION

The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the invention.

In one embodiment, a dome connector for a flywheel rim to shaft attachment is provided. The dome connector includes a helically wound composite band that extends from a first port to a second port. The helically wound composite band has a helical angle in relation to a line perpendicular to a center of axis of the dome connector. The helical angle is selected to, at least in part, achieve a desired stiffness in the dome connector.

In another embodiment, a flywheel is provided. The flywheel includes a metal shaft, a composite flywheel rim and a dome connector. The dome connector couples the composite flywheel to the metal shaft. The dome connector includes a helically wound composite band that extends from a first port to a second port. The helically wound composite band has a helical angle in relation to a line perpendicular to a center of axis of the dome connector. A deflection characteristic of the dome connector generally matching a deflection characteristic of the flywheel rim.

In still another embodiment, a method of forming a coupling between a composite flywheel rim and a metal shaft is provided. The method includes: laying up a continuous band of composite fibers in a helical pattern from a first port to a second port to form a central passage with a first band layer; laying up subsequent layers with the continuous band of composite fibers over at least a portion of the first band layer to form a body; and curing the composite fibers to form a dome connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more easily understood and further advantages and uses thereof will be more readily apparent, when considered in view of the detailed description and the following figures in which:

FIG. 1A is a front perspective view of a flywheel assembly of one embodiment of the present invention;

FIG. 1B is a cross-sectional side view of the flywheel assembly of FIG. 1A;

FIG. 2A is a side view of the dome connector of one embodiment of the present invention;

FIG. 2B is a cross-sectional side view of a dome connector of FIG. 2A;

FIG. 3 is a side view illustrating the forming of a dome connector of one embodiment of the present invention;

FIG. 4 is a side view of a flywheel assembly with a dome connector configuration of one embodiment of the present invention;

FIG. 5A is a cross-sectional side view of a flywheel assembly of one embodiment of the present invention;

FIG. 5B is a close up view of a portion of the flywheel assembly of FIG. 5A;

FIG. 6A is a side view of another flywheel assembly being formed of one embodiment of the present invention;

FIG. 6B is a cross-sectional side view of another flywheel assembly of an embodiment of the present invention;

FIG. 7 illustrates a flywheel forming diagram of one embodiment;

FIG. 8 illustrates a flywheel forming diagram of another embodiment;

FIG. 9 illustrates a shaft connecting diagram of one embodiment;

FIG. 10 illustrates a shaft connecting diagram of another embodiment;

FIG. 11 illustrates a shaft connecting diagram of yet another embodiment; and

FIG. 12 is a partial side view of a flywheel assembly of one embodiment of the present invention.

In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof.

Embodiments of the present invention provide a filament wound composite dome connector used for a flywheel rim to metal shaft connection. In embodiments, at least some of the filaments that make up the composite material that form the dome connector have winding patterns that are generically referred to herein as helically wound. Helically wound patterns include polar, planar or other opening to opening wind patterns used to form the domes. Hence, the term “helically wound” is a generic term that is used throughout the specification and claims that includes polar, planar and other opening to opening wind patterns used to form the domes. The helically wound dome connectors are able to strain with the rim, yet maintain dynamic stiffness. The dome connectors also minimize the stress concentrations placed on an inside diameter of the flywheel rim, which can be significant in other type rim-shaft connections, such as hubs, that are known in the art. This reduction/elimination of stress concentrations is important since the energy storage capacity of a flywheel is directly related to the maximum stress in the flywheel rim. Moreover, the compliance of the dome connectors allow for a match between a deflection in the dome connector (dome connector deflection) and deflection in the flywheel rim (flywheel deflection) that is encountered during rotation of the flywheel. In embodiments, dome connector geometry, fiber material type, material fiber thickness and wind angle of the fiber are tailored to achieve the desired deflection or stiffness required for a specific design. As discussed below in detail, dome connectors may be wound in place with the flywheel rim or post installed by: bonding, a press fitting, shrink fitting and the like. Post installing of the dome connectors allow for the use of a single dome or two or more dome connectors per flywheel rim. Additionally, in a multi-dome connector configuration, the orientation of the domes relative to each other can be in a convex-convex, concave-concave or concave-convex configuration as also discussed below.

Referring to FIG. 1A, a front perspective view of a flywheel assembly 100 of an embodiment that includes a fly wheel rim 104, a dome connector 200 and a metal shaft 102 is provided. As illustrated, the flywheel rim 104 is coupled to the shaft 102 via dome connector 200. A cross-sectional side view of the flywheel assembly is further illustrated in FIG. 1B. The dome connector 200 is coupled to the shaft 102 via attachment collars 105 a and 105 b in this embodiment. The attachment collars 105 a and 105 b are further discussed below in regards to FIG. 12. An illustration of an embodiment of a dome connector 200 is provided for in the side view or FIG. 2A and the cross-sectional side view of FIG. 2B. This embodiment of the connector dome 200 includes an outer surface 202 that is formed in a desired shape. A central passage 204 passes through the dome connector 200. At the opposed entrances to passage 204 in the dome connector 200 are respective first and second openings 204 a and 204 b (first port and second port). In embodiments, the dome connector 200 has a dome length 220 extending along a distance of the central passage 204 and a dome diameter 227 extending a distance perpendicular to the central passage 204. In the embodiments of FIGS. 2A and 2B, the distance of the dome length. 220 is less than the distance of the dome diameter 227. In other embodiments, the dome length 220 would be greater than or equal to the distance of the dome diameter 227.

The formation of a dome connector 200, such as dome connector 200 of FIG. 1A, is discussed in regards to FIG. 3. FIG. 3 illustrates a tool 300 in which a dome connector is formed in one embodiment. The dome connector 200 is made from a band of toes 306. Each toe consisting of thousands of fibers such as, but not limited to, carbon and heat activated material such as pre-preg material that is known in the art. The band 306 is wound around the tool 300 to form the desired dome shape. In particular, in one embodiment the band is positioned by a band dispensing system (not shown), that is known in the art, that includes a band dispensing head that selectively positions the band via controller (not shown). The tool 300 is coupled to a portion of the dispensing system that rotates the tool 300 about the tool's center of axis 308 while the band dispensing head is moved axially, in relation to the tool, by the controller. Lines 310 a and 310 b are known as the tangent lines of the tool 300 that define a cylindrical portion 300 a of the tool 300 from domes 300 a and 300 b of the tool 300. Between the tangent lines 310 a and 310 b is called inboard and outside the tangent line 310 a and 310 b is called outboard. In the embodiment of FIG. 3, overlaying hoop bands 312 are positioned over the cylindrical portion 300 a of the tool 300. In one embodiment, the hooped bands 312 are not only applied to the cylindrical portion 300 a but also outboard of at least one of the tangent lines 310 a and 310 b down the respective at least one dome 300 a and/or 300 c of the tool 300.

Embodiments start the band 306 at a first opening (port) position 302 a and then wind the band around the tool with the dispensing system to the second port 302 b at a select helical angle 304 to form a select helical pattern from one port 304 a to the other port 304 b in the finished dome connector. FIG. 3 illustrates adjacent band loops having gaps for illustration purposes. In practice, as the band 306 is being laid out on the tool in the helical pattern, there will be no gaps and no overlays (within a layer being formed) that would weaken the dome connector 200. When the band 306 reaches the second port 304 b the dispensing head will reverse direction and lay down another helical pattern layer over the first helical pattern layer to the first port 304 a. Further helical patterned layers are layered up on the tool to form the dome connector 200. Hence, the dome connector 200 will consist of multi helical patterned band layers. Specific dome geometries are achieved by winding on tools with different contours. As discussed above, the helical angle 304 is one variable that can be selected to achieve a desired characteristic of the dome connector 200 such as providing a matching deflection (or stiffness) with an associated flywheel rim 104.

As discussed above, embodiments of the dome connector are effective because they are made with material that has low density but high strength and can be tailored to the stiffness of the flywheel rim 104 by changing any one of the helical angles in the helical pattern, the geometry of the dome and the type of fiber used. Additionally, in domes which use more than one helically wound layer, one or more of the layers may be wound with a pull-back, which is winding the helical to some radius larger than the radius of the ports/collars. Using pull backs can effectively tailor the stiffness and strength of the dome and port region. Regarding the geometry, by changing the contour of the dome to either relatively shallow or relatively deep, a desired stiffness or deflection can be achieved to match an associated flywheel rim 104. As discussed above, the dome connector can have either convex or concave ends and two or more dome connectors can be used per flywheel rim. For example, please refer to FIG. 4 where a flywheel assembly 400 having four dome connectors 410, 420, 430 and 440 is illustrated. The four dome connectors 410, 420, 430 and 440 of the flywheel assembly 400 are positioned next to each other with their respective inner passages aligned. The shaft 102 is mounted within the aligned inner passages of the four dome connectors 410, 420, 430 and 440. The flywheel rim 104 is fitted around the four dome connectors 410, 420, 430 and 440. As discussed above, the dome connectors can have ends in different configurations (i.e. convex ends or concave ends) and embodiments are not limited to specific configurations or the number of dome connectors used in a flywheel assembly.

FIG. 5A illustrates a cross-sectional side view of a flywheel assembly 500 that includes dome connectors 502 a and 502 b of an embodiment. In this embodiment, y-joint connectors 220 are further used to couple the flywheel rim 104 to the dome connectors 502 a and 502 b. The connectors 220 are positioned between the flywheel 104 and the respective dome connectors 502 a and 502 b where the respective dome begins to curve away from the rim 104. A close up view 221 of a y-joint connector 220 is illustrated in FIG. 5B. The connectors 220 can be fabricated from rubber, elastomer, adhesive or other suitable material. The connectors can be either co-fabricated with the flywheel-dome assembly 500 or after the domes 502 a and 502 b are installed in the flywheel 104.

The forming of flywheel assemblies is further discussed below. In one embodiment, a dome connector (such as dome connector 200 of FIG. 2A) is first formed. A center cylindrical portion is then removed from the dome connector. Referring to FIG. 6A, the formation of a flywheel assembly 600 is illustrated. In this side view illustration, a dome connector is first formed and its center cylindrical portion is removed. The dome portions 602 a and 602 b of the dome connector is then positioned as illustrated with a shaft 102 extending through central aligned openings of the dome portion 602 a and 602 b. Temporary winding mandrels 604 a and 604 b are positioned in relation to the dome portions 602 a and 602 b. The winding mandrels 604 a and 604 b and portion of the dome portions 602 a and 602 b create a forming surface in which the flywheel rim 104 is wound around and formed. Once the flywheel rim is formed 104, the winding mandrels 604 a and 604 b are removed. This embodiment allows for flywheels with smaller diameters. FIG. 6B illustrates another way of forming a flywheel assembly 620. In this assembly 620, the dome portions 602 a and 602 b are first cured and then placed and bonded inside of a pre-cured flywheel 104.

A flywheel assembly forming diagram 700 of an embodiment is illustrated in FIG. 7. In this embodiment, the process starts by positioning a band dispensing head in relation to a tool (702). The tool is then rotated (704) and a continuous band is applied to the tool in a select pattern (706). As discussed above, the toe (or band) is laid down from one opening (or port) to the other port in a helical pattern having a select helical angle for at least a portion of the dome connector. Once the entire dome connector has been laid up, it is cured (708). The dome connector is then removed from the tool (710) and in this embodiment is inserted in a central passage in a cured flywheel rim (712) (similar to the discussion in regards to the embodiment of FIG. 6B). The dome connector is bonded with an adhesive within the central passage of the cured flywheel (714). Another embodiment of forming a flywheel assembly is illustrated in the flywheel assembly forming diagram 800 of FIG. 8. In this embodiment, the band or band dispensing head is positioned in relation to the tool (802). Once the dispensing head is in position, the tool is rotated (804). A continuous length of band is then applied on the tool in a select pattern to form the dome connector shape (806). In this embodiment, the flywheel rim is then formed over the dome connector (808) (similar to the discussion in regards to the embodiment of FIG. 6 where the flywheel may be built to extend past the tangent lines of the dome connector). This can be done with the use of the dispensing head or other methods known in the art for forming composite material. The dome connector and the flywheel rim are then cured together therein coupling the dome connector to the flywheel rim (810). In an embodiment, the cured flywheel rim and dome connector are then removed from the tool (812). The dome connector would then be connected to the shaft.

Connecting the dome connector to the shaft can be done in a number of ways. For example, in the embodiment of the shaft connecting diagram 900 of FIG. 9, the dome is formed on a shaft 102. In particular, in this embodiment, an attachment collar (such as attachment collar 105 of FIG. 12) is first placed on a shaft 102 (902). An adhesive is then placed on the collar 105 (903). The shaft 102 is then rotated (904). The continuous band is then dispensed on the adhesive on the collar in the helical pattern to form the dome connector (906). The dome connector is then cured and the adhesive bonds the dome connector to the collar 105 (908). In another embodiment, illustrated in the shaft connecting diagram 1000 of FIG. 10, the dome connector is formed on the tool as discussed above (1002). The dome connector is then cured (1004). The dome connector is then removed from the tool (1006). An adhesive is placed on the collar (1008). The dome connector is positioned on the shaft (1010). The adhesive is then cured to bond the dome connector to the collar (1012). This collar would then interface with a shaft used for flywheel operation. In embodiments, the adhesive may cure by heat, by drying out and the like. In another example, as illustrated in the shaft connecting diagram (1100) of FIG. 11, the dome connector is formed on the tool as generally described above (1102). The dome connector is then cured (1104). Once cured, the dome connector is removed from the tool (1106). The shaft that the dome connector is to be mounted to is then cooled which will cause it to contract (1108). While the shaft is cooling, the dome connector receives the shaft in its central passage (1110). The shaft is then allowed to heat, which causes the shaft to expand and bond in the central passage of the dome connector (1112). The above provides some example methods of coupling the dome connector to the shaft and the flywheel rim to the dome connector.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof. 

1. A dome connector for a flywheel rim to shaft attachment comprising: a helically wound composite band extending from a first port to a second port, the helically wound composite band having a helical angle in relation to a line perpendicular to a center of axis of the dome connector, the helical angle selected to at least in part achieve a desired stiffness in the dome connector.
 2. The dome connector of claim 1, further comprising: the helically wound composite band forming a body having a first end, a second end and a mid cylindrical portion positioned between the first end and the second end, the body further having a central passage, the central passage opening to the respective first and second ports.
 3. The dome connector of claim 2, wherein at least one of the first end and the second end of the body is formed generally in a convex shape.
 4. The dome connector of claim 2, wherein at least one of the first end and the second end of the body is placed such that the dome is concave shaped.
 5. The dome connector of claim 2, wherein the desired stiffness of the body is further achieved by forming a select shape of the dome connector.
 6. A flywheel assembly comprising: a metal shaft; a composite flywheel rim; and a dome connector coupling the composite flywheel to the metal shaft, the dome connector including, a helically wound composite band extending from a first port to a second port, the helically wound composite band having a helical angle in relation to a line perpendicular to a center of axis of the dome connector, a deflection characteristic of the dome connector generally matching a deflection characteristic of the flywheel rim.
 7. The flywheel assembly of claim 6, wherein the helical angle is selected to at least in part achieve the generally matching deflection characteristic of the flywheel rim.
 8. The flywheel assembly of claim 6, wherein the dome connector further comprises: the helically wound composite band forming a body having a first end, a second end and a mid cylindrical portion positioned between the first end and the second end, the body further having a central passage, the central passage opening to the respective first and second ports.
 9. The flywheel assembly of claim 8, wherein at least one of the first end and the second end of the body is formed generally in a convex shape.
 10. The flywheel assembly of claim 9, wherein the flywheel rim has a portion that engages the at least one of the first end and the second end of the body that is generally in the convex shape.
 11. The flywheel assembly of claim 8, wherein at least one of the first end and the second end of the body is placed within the flywheel rim such that they are in a generally concave shape.
 12. The flywheel assembly of claim 8, wherein the body has a select length and a select diameter, the select length and diameter selected for the application.
 13. The flywheel assembly of claim 8, wherein the desired stiffness of the body is further achieved by forming a select shape of the dome connector.
 14. A method of forming a coupling between a composite flywheel rim and a metal shaft, the method comprising: laying up a continuous band of composite fibers in a helical pattern from a first port to a second port to form a central passage with a first band layer; laying up subsequent layers with the continuous band of composite fibers over at least a portion of the first band layer to form a body; and curing the composite fibers to form a dome connector.
 15. The method of claim 14, further comprising: bonding an attaching collar within the central passage of the dome connector; and bonding the dome connector within a central passage of the composite flywheel rim.
 16. The method of claim 15, wherein bonding the dome connector within the central passage of the composite flywheel rim further comprises: forming the flywheel rim over the dome connector; and curing the flywheel rim and the dome connector simultaneously.
 17. The method of claim 15, wherein bonding the dome connector within the central passage of the composite flywheel rim further comprises: applying an adhesive between the dome connector and the central passage of the composite flywheel rim.
 18. The method of claim 15, wherein bonding the metal shaft within the center of the dome connector further comprises: applying an adhesive between the metal passage and the central passage of the dome connector.
 19. The method of claim 15, wherein bonding the metal shaft within the central passage of the dome connector further comprises: cooling the metal shaft; placing the cooled shaft in the central passage of the dome connector; and heating up the metal shaft.
 20. The method of claim 14, further comprising: removing a central portion of the continuous band of composite fibers. 